The Evidence Base for Diabetes Care SECONDEDITION The Evidence Base for Diabetes Care, Second Edition E d i te d by William H. Herman, Ann Louise Kinmonth, Nicholas J. Wareham and Rhys Williams © 2010 John Wiley & Sons, Ltd. ISBN: 978-0-470-03274-9 The Evidence Base for Diabetes Care SECOND EDITION EDITED BY William H. Herman Department of InternalMedicineandEpidemiology,University of Michigan, AnnArbor, MI, USA Ann Louise Kinmonth Department of Public Health andPrimary Care,Instituteof Public Health, Cambridge,UK Nicholas J. Wareham MRCEpidemiology Unit, Instituteof Metabolic Science,Addenbrooke’s Hospital, Cambridge,UK Rhys Williams Schoolof Medicine, SwanseaUniversity, Swansea, UK Thiseditionfirstpublished2010(cid:1)2010,JohnWiley&SonsLtd. Wiley-BlackwellisanimprintofJohnWiley&Sons,formedbythemergerofWiley’sglobalScientific,TechnicalandMedical businesswithBlackwellPublishing. Registeredoffice:JohnWiley&SonsLtd,TheAtrium,SouthernGate,Chichester,WestSussex,PO198SQ,UK OtherEditorialOffices: 9600GarsingtonRoad,Oxford,OX42DQ,UK 111RiverStreet,Hoboken,NJ07030-5774,USA Fordetailsofourglobaleditorialoffices,forcustomerservicesandforinformationabouthowtoapplyforpermission toreusethecopyrightmaterialinthisbookpleaseseeourwebsiteatwww.wiley.com/wiley-blackwell TherightoftheauthortobeidentifiedastheauthorofthisworkhasbeenassertedinaccordancewiththeCopyright, DesignsandPatentsAct1988. Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmitted,inanyformor byanymeans,electronic,mechanical,photocopying,recordingorotherwise,exceptaspermittedbytheUKCopyright, DesignsandPatentsAct1988,withoutthepriorpermissionofthepublisher. Wileyalsopublishesitsbooksinavarietyofelectronicformats. Somecontentthatappearsinprintmaynotbeavailable inelectronicbooks. Designationsusedbycompaniestodistinguishtheirproductsareoftenclaimedastrademarks.Allbrandnamesand productnamesusedinthisbookaretradenames,servicemarks,trademarksorregisteredtrademarksoftheirrespective owners.Thepublisherisnotassociatedwithanyproductorvendormentionedinthisbook.Thispublicationisdesignedto provideaccurateandauthoritativeinformationinregardtothesubjectmattercovered.Itissoldontheunderstandingthat thepublisherisnotengagedinrenderingprofessionalservices.Ifprofessionaladviceorotherexpertassistanceisrequired, theservicesofacompetentprofessionalshouldbesought. Thecontentsofthisworkareintendedtofurthergeneralscientificresearch,understanding,anddiscussiononlyandarenot intendedandshouldnotberelieduponasrecommendingorpromotingaspecificmethod,diagnosis,ortreatmentby physiciansforanyparticularpatient.Thepublisherandtheauthormakenorepresentationsorwarrantieswithrespecttothe accuracyorcompletenessofthecontentsofthisworkandspecificallydisclaimallwarranties,includingwithoutlimitation anyimpliedwarrantiesoffitnessforaparticularpurpose. Inviewofongoingresearch,equipmentmodifications,changes ingovernmentalregulations,andtheconstantflowofinformationrelatingtotheuseofmedicines,equipment,anddevices, thereaderisurgedtoreviewandevaluatetheinformationprovidedinthepackageinsertorinstructionsforeach medicine,equipment,ordevicefor,amongotherthings,anychangesintheinstructionsorindicationofusageandforadded warningsandprecautions. Readersshouldconsultwithaspecialistwhereappropriate. Thefactthatanorganizationor Websiteisreferredtointhisworkasacitationand/orapotentialsourceoffurtherinformationdoesnotmeanthattheauthor orthepublisherendorsestheinformationtheorganizationorWebsitemayprovideorrecommendationsitmaymake. Further,readersshouldbeawarethatInternetWebsiteslistedinthisworkmayhavechangedordisappearedbetweenwhen thisworkwaswrittenandwhenitisread. Nowarrantymaybecreatedorextendedbyanypromotionalstatementsforthis work.Neitherthepublishernortheauthorshallbeliableforanydamagesarisingherefrom. LibraryofCongressCataloging-in-PublicationData Theevidencebasefordiabetescare/editedbyW.Herman...[etal.].–2nded. p.;cm. Includesbibliographicalreferencesandindex. ISBN978-0-470-03274-9(hb) 1. Diabetes–Treatment.2. Evidence-basedmedicine. I.Herman,William [DNLM:1. DiabetesMellitus–therapy.2. Diabetes Complications–prevention&control.3. DiabetesComplications–therapy.4. DiabetesMellitus–prevention&control.5. Evidence-BasedMedicine. WK815 E9292010] RC660.E9252010 616.4’62–dc22 2009031441 ISBN:9780470032749(HB) AcataloguerecordforthisbookisavailablefromtheBritishLibrary. Setin9.5/12PtPalatinobyThomsonDigital,Noida,India. PrintedinSingaporebyFabulousPrintersPteLtd. FirstImpression 2010 Contents ListofContributors,vii 8 Whatistheevidencethatchangingtobacco usereducestheincidenceofdiabetic complications?,161 1 Theevidencebasefordiabetescare,1 DeborahL.Wingard,ElizabethBarrett-Connor, WilliamH.Herman,AnnLouiseKinmonth, NicoleM.Wedick NicholasJ.Wareham,RhysWilliams 9 Doesintensiveglycaemicmanagementreduce morbidityandmortalityintype1diabetes?,178 WilliamH.Herman Part1: Evidence-based definition 10 Doesintensiveglycaemicmanagementreduce and classification morbidityandmortalityintype2diabetes?,189 AmandaI.Adler 2 Classificationofdiabetes,9 MaximiliandeCourten 11 Glycaemiccontrolandotherinterventionsinthe treatmentofgestationaldiabetes,199 3 Commentaryontheclassificationanddiagnosis DavidR.McCance ofdiabetes,25 StephenO’Rahilly,NicholasJ.Wareham 12 Antihypertensivetherapytopreventthe cardiovascularcomplicationsofdiabetes mellitus,226 Part2: Primary and primordial prevention TonyaL.Corbin,AlanB.Weder and early detection 13 Doestreatinghyperlipidaemia withmedication preventcomplications?,241 4 Preventionoftype1diabetes,31 HelenM.Colhoun JayS.Skyler 14 Othercardiovascularriskfactors,256 5 Preventionoftype2andgestational StephenThomas,GianCarloViberti diabetes,49 15 Preventionoftheconsequencesofdiabetes–a RichardF.Hamman,DanaDabelea commentary,266 6 Theevidencetoscreenfortype2diabetes,111 HertzelC.Gerstein MichaelM.Engelgau,K.M.VenkatNarayan Part4: Treatment of established Part3: Prevention of complications complications 7 Theeffectivenessofinterventionsaimedatweight 16 Treatmentofdiabeticretinopathy,275 lossandothereffectsofdietandphysicalactivityin AyadAl-Bemani,RoyTaylor achievingcontrolofdiabetesandpreventingits 17 Preventionandtreatmentofdiabeticnephropathy: complications,137 theroleofbloodpressurelowering,285 NitaGandhiForouhi,NicholasJ.Wareham CarlErikMogensen v Contents 18 Treatmentofestablishedcomplications: Part 5: Self-management, healthcare periodontaldisease,291 organization and public policy GeorgeW.Taylor,WencheS.Borgnakke 19 Treatmentofdiabeticneuropathy,317 25 Whatistheevidencethatincreasingengagementof RodicaPop-Busui,ZacharySimmons,EvaL.Feldman individualsinself-managementimprovesthe 20 Treatmentoferectiledysfunction,341 processesandoutcomesofcare?,421 DavidE.Price,GeoffreyHackett DebraL.Roter,AnnLouiseKinmonth 21 Cardiaccomplicationsandmanagement,355 26 Deliveringcaretothepopulation,438 AnthonyS.Wierzbicki,SimonR.Redwood RhysWilliams,AnnJohn,AmbadyRamachandran, 22 Thetreatmentofestablishedcomplications: ChamukuttanSnehalatha cerebrovasculardisease,377 27 Cost-effectivenessofinterventionsforthe DevinL.Brown,SusanL.Hickenbottom, preventionandcontrolofdiabetes,449 TeresaL.Jacobs RuiLi,PingZhang 23 Themanagementofperipheralarterialdiseasein 28 Theroleofpublicpolicy,471 patientswithtype2diabetes,393 JuliaCritchley,NigelUnwin SydneyA.Westphal,PasqualeJ.Palumbo 24 Epidemiologyoffootulcersandamputationsin Index,489 peoplewithdiabetes:evidenceforprevention,403 GayleE.Reiber,WilliamR.Ledoux vi List of Contributors Amanda I.Adler Julia Critchley Richard F. Hamman MRCEpidemiologyUnit InstituteofHealthandSociety DepartmentofPreventiveMedicineand InstituteofMetabolicScience NewcastleUniversity Biometrics Addenbrooke’sHospital NewcastleuponTyne,UK UniversityofColoradoHealthSciences Cambridge,UK Center Dana Dabelea Denver,CO,USA Ayad Al-Bemani DepartmentofPreventiveMedicineand DepartmentofOpthamology Biometrics William H.Herman RoyalVictoriaInfirmary UniversityofColoradoHealthSciences DepartmentofInternalMedicineand NewcastleuponTyne,UK Center Epidemiology Elizabeth Barrett-Connor Denver,CO,USA UniversityofMichigan AnnArbor DepartmentofFamilyandPreventive Michael M. Engelgau MI,USA Medicine DivisionofDiabetesTranslation UniversityofCalifornia,SanDiego CenterforDiseaseControland Susan L. Hickenbottom LaJolla,CA,USA Prevention StJosephMercyHospital Wenche S. Borgnakke Atlanta,GA,USA AnnArbor DepartmentofCariology,Restorative MI,USA SciencesandEndodontics Eva L. Feldman UniversityofMichiganSchoolof UniversityofMichigan TeresaL. Jacobs Dentistry AnnArbor,MI,USA DepartmentsofNeurosurgeryand AnnArbor,MI,USA Neurology Nita GandhiForouhi UniversityofMichigan Devin L. Brown ElsieWiddowsonLaboratory AnnArbor StJosephMercyHospital MRCEpidemiologyUnit MI,USA AnnArbor,MI,USA Cambridge,UK Ann John Helen M. Colhoun Hertzel C.Gerstein TheSchoolofMedicine DepartmentofGeneticEpidemiology DepartmentofMedicineandthe UniversityofWalesSwansea UniversityCollegeDublin PopulationHealthResearch Swansea,UK Belfield,Dublin,Ireland Institute McMasterUniversityandHamilton Ann Louise Kinmonth Tonya L. Corbin HealthSciences GeneralPracticeandPrimaryCare DivisionofCardiovascularMedicine Hamilton,ON,Canada ResearchUnit DepartmentofInternalMedicine DepartmentofPublicHealthand UniversityofMichigan Geoffrey Hackett PrimaryCare AnnArbor,MI,USA GoodHopeHospital UniversityofCambridge SuttonColdfield Cambridge,UK Maximilian de Courten WestMidlands,UK SchoolofExerciseandNutritionSciences FacultyofHealthandBehaviouralSciences MonashUniversity Burwood,Victoria,Australia vii ListofContributors William R. Ledoux Ambady Ramachandran Stephen Thomas VARehabilitationResearchand IndiaDiabetesResearchFoundationand DiabetesCentre DevelopmentCenterforExcellencein DrARamachandran’sDiabetes StThomas’Hospital LimbLoss Hospitals London,UK PreventionandProsthetic Egmore Engineering Chennai,India Nigel Unwin VAPugetSound,and InstituteofHealthandSociety Simon R. Redwood DepartmentofOrthopaedicsandSports NewcastleUniversity Medicine DepartmentofCardiology NewcastleuponTyne,UK UniversityofWashington Guy’sandStThomas’Hospitals Seattle,WA,USA London,UK GianCarlo Viberti DepartmentofDiabetesand Rui Li GayleE. Reiber Endocrinology CentersforDiseaseControland VAHealthServicesResearchand KCLGuy’sHospital Prevention DevelopmentandVARehabilitation London,UK Atlanta,GA,USA ResearchandDevelopmentCenterfor ExcellenceinLimbLossPrevention Nicholas J. Wareham David R. McCance andProstheticEngineering MRCEpidemiologyUnit,Instituteof RegionalCentreforEndocrinologyand VAPugetSound,and MetabolicScience,Addenbrooke’s Diabetes DepartmentofHealthServicesand Hospital,Cambridge,UK Belfast,UK Epidemiology UniversityofWashington Alan B.Weder CarlErik Mogensen Seattle,WA,USA DivisionofCardiovascularMedicine DepartmentofInternalMedicineM DepartmentofInternalMedicine Debra L. Roter (DiabetesandEndocrinology) UniversityofMichigan DepartmentofHealthPolicyandManagement AarhusUniversityHospital AnnArbor,MI,USA JohnsHopkinsSchoolofPublicHealth Aarhus,Denmark Baltimore,MD,USA Nicole M.Wedick K.M. VenkatNarayan DepartmentofFamilyandPreventive Zachary Simmons DivisionofDiabetesTranslation Medicine PennsylvaniaStateUniversityCollegeof CenterforDiseaseControland UniversityofCalifornia,SanDiego Medicine Prevention LaJolla,CA,USA Hershey,PA,USA Atlanta,GA,USA Sydney A.Westphal Jay S. Skyler Stephen O’Rahilly DepartmentofMedicine DivisionofEndocrinology,Diabetesand DepartmentofClinicalBiochemistry MaricopaMedicalCenter Metabolism SchoolofClinicalMedicine Phoenix,AZ,USA UniversityofMiami CambridgeUniversity Miami,FL,USA Addenbrooke’sHospital Anthony S. Wierzbicki Cambridge,UK Chamukuttan Snehalatha DepartmentofChemicalPathology Guy’sandStThomas’Hospitals IndiaDiabetesResearchFoundationand Pasquale J.Palumbo London,UK DrARamachandran’sDiabetes DepartmentofMedicine Hospitals MayoClinic Rhys Williams Egmore Scottsdale,AZ,USA SchoolofMedicine Chennai,India SwanseaUniversity RodicaPop-Busui Swansea,UK George W. Taylor DepartmentofInternalMedicine DepartmentofCariology,Restorative DivisionofMetabolism,Endocrinology Deborah L. Wingard SciencesandEndodontics andDiabetes DepartmentofFamilyandPreventive UniversityofMichiganSchoolof UniversityofMichiganMedicalCenter Medicine Dentistry AnnArbor,MI,USA UniversityofCalifornia,SanDiego AnnArbor,MI,USA LaJolla,CA,USA David E. Price Roy Taylor ABMUniversityTrust Ping Zhang SchoolofClinicalMedicalSciences MorristonHospital CentersforDiseaseControland MedicalSchool Swansea,UK Prevention NewcastleUniversity Atlanta,CA,USA NewcastleuponTyne,UK viii 1 The evidence base for diabetes care William H. Herman1, Ann Louise Kinmonth2, Nicholas J. Wareham3, Rhys Williams4 1DepartmentofInternalMedicineandEpidemiology,UniversityofMichigan,AnnArbor,MI,USA 2GeneralPracticeandPrimaryCareResearchUnit,DepartmentofPublicHealthandPrimaryCare, UniversityofCambridge,Cambridge,UK 3MRCEpidemiologyUnit,InstituteofMetabolicScience,Addenbrooke’sHospital,Cambridge,UK 4SchoolofMedicine,SwanseaUniversity,Swansea,UK Evidence-based medicine onlyintheirexposuretotheinterventionand,hence, differences in observed outcomes can be attributed A complex set of decisions by individuals and orga- todifferencesintheintervention. nizations determine how health care is delivered to Perhaps not surprisingly, the major limitation of peoplewithdiabetes.Historically,suchdecisionshave RCTsliesintheirexternalvalidity,thatis,theextent beenmadeintheabsenceofevidenceorwithoutstrict towhichtheyaregeneralizabletoparticularpopula- regardtoit.Thishasledtothepersistenceofpractices tion groups, individuals, practitioners and settings. forwhichthereislittleevidence,theslowadoptionof ‘Efficacy’ is defined by Last as the extent to which a new practices that have been demonstrated to be specific intervention produces a beneficial result effective and wide variation in clinical practice and under ideal conditions.2 ‘Effectiveness’, on the other the quality of care. In recent years, there has been hand,istheextenttowhichtheinterventiondoeswhat increasing appreciation that treatment decisions itisintendedtodo‘intherealworld’.2Whenindivi- shouldbebasedonsoundevidence.Forpatients,care dualswhoparticipateinRCTsareatypical,thehealth providers and health systems alike, this awareness care professionals who participate are unrepresenta- representsanopportunitytoshapethedeliveryofcare tive or the settings deviate from a usual clinical en- onthebasisofevidenceofeffectiveness.Thisbookis vironment,theexternalvalidityorgeneralizabilityof devoted to providing the evidence base on which the results of the RCT may be low. Indeed, in most treatmentdecisionsindiabetescaremaybemade. instances,anRCToffersanindicationoftheefficacyof Sackett et al. defined evidence-based medicine as an intervention, what can be achieved in the most ‘theconscientious,explicitandjudicioususeofclini- favourablecircumstances,ratherthanitseffectiveness, cally relevant research in making decisions about whatcanbeachievedineverydayclinicalpractice. the care of individual patients’.1 The strength of Another limitation of evidence-based medicine is evidence-based medicine is that it moves clinical that the evidence that we need is not always avail- practice from anecdotal experience and expert opi- able.Insomeinstances,lackofevidenceisaresultof niontoarefutablescientificfoundationofbasicand thenecessarystudiesnothavingbeencarriedoutor clinical research from which we can systematically not having been carried out for long enough to progress. Evidence-based medicine advocates that evaluate health endpoints. The task of conducting experimentalmethods,especiallyrandomized,con- alloftherequiredRCTsisoverwhelming.Therearea trolled clinical trials (RCTs), provide the basis for huge number of health care interventions which, clinical practice. The strength of RCTs lies in their when added together, have many components. It is internal validity. The use of randomization is the simplyimpossibletosubjectalloftheseinterventions strongestinsurancethattreatmentgroupswilldiffer and their components to experimental evaluation. The Evidence Base for Diabetes Care, Second Edition E d i te d by William H. Herman, Ann Louise Kinmonth, Nicholas J. Wareham and Rhys Williams © 2010 John Wiley & Sons, Ltd. ISBN: 978-0-470-03274-9 1 CHAPTER 1 Theevidencebasefordiabetescare Some interventions are studied and some are not. positivemessage of evidence-based medicine can,if Indeed,sometypesofinterventionsaremorelikelyto takentoextremes,becomeaformof‘evidence-based bestudiedthanothers.Forexample,pharmacological paralysis’,whichactstothedetrimentofthepatient interventionsarestudiedmoreextensivelythannon- andthepopulation. pharmacological interventions, because of regulatory requirementsandindustrysupportandbecauseofthe technicalandmethodologicaldifficultiesindesigning Evidence-based practice RCTstoevaluatenon-druginterventions.Asaresult, theliteratureoftenfailstoprovideconvincingevidence Forthesereasons,weprefertheterm‘evidence-based forcomplexbehaviouralinterventionssuchaseduca- practice’tothenarrower,butmorewidelyusedterm, tion,dietandlifestylemodification.Inotherinstances, ‘evidence-based medicine’. Evidence-based practice RCTs may be impossible to conduct if, for example, emphasizes the importance of practitioners other thereareethicalorlegalobstacles,ifsomeinterventions than doctors and the importance of health-related cannotbeallocated on a random basisorif potential activitiesotherthanthosemostobviouslyassociated participants, practitioners or investigators refuse to withphysicians.Indefiningevidence-basedpractice, takepart. threecomponentsareessential: Another limitation of evidence-based medicine derives from an understanding of the limits of the . the determination, whenever possible, to base scientific method in clinical practice. Clinical deci- decisionsonevidenceaccumulatedthroughresearch sions involve people and the application of results . use of the best possible evidence available at the from research to clinical practice must take account timethedecisionneedstobemadeand ofpeopleintheirsocialcontext.3Clinicaljudgement . useoftheevidencemostappropriatetoaparticular is central to clinical practice and involves weighing patientorpopulation. the benefits and risks of any medical choice in consultation with individual patients. Clinical trials Wewouldwidenthatdefinitionofevidence-based explicitly focus on hard endpoints such as physio- practicetoincludepeoplewhoarenotyetpatientsand logicalmeasuresanddiseaseincidenceormortality. mayneverbecomepatients,thatis,toincludepreven- They often fail to focus on soft endpoints such as tionaswellascare,cureandrehabilitation.Inaddition, patient preferences or quality of life. To the extent although evidence-based practice uses the evidence that the latter influence clinical decision making, fromRCTstoprovideevidenceforclinicalpractice,it non-scientific mechanisms may guide decisions.3 doesnotdiminishtheimportanceofhumanrelation- Indeed, as stated by Sackett et al., ‘External clinical ships or ignore the fact that clinical decisions in evidence can inform, but can never replace, indivi- primary care involve consideration of the unique dual clinical expertise. It is this expertise that problemsandconcernsofindividualpatients. decides whether the external evidence applies to Wehavechosentocallthisbook‘TheEvidenceBase theindividualpatientatalland,ifso,howitshould forDiabetesCare’toemphasize,fromtheoutset,that be integrated into a clinical decision. Any external ourfocusisontheextenttowhichdiabetesprevention guidelinemustbeintegratedwithindividualclinical andtreatmentcanbebasedonhigh-qualityevidence. expertiseindecidingwhetherandhowitmatchesthe Itisnotintendedtobeacomprehensivetextbookon patient’s clinical state, predicament and preferences how to care for people with diabetes. Although it andthuswhetheritshouldbeapplied.’1 refers to clinical guidelines, it is not a collection of One of the ‘credibility gaps’ developing between evidence-based guidelines. This book sets out to ex- the advocates of evidence-based medicine and the amine critically the best evidence that is currently practitioners engaged in day-to-day patient care is availableinthefieldofdiabetespreventionandcare that studies which faithfully reflect the clinical and andtopresentitinanaccessibleform.Theenormous behavioural complexities of individual patients not potentialofevidence-basedpracticetopreventillness, onlyhavenotyetbeendonebutareunlikelyevertobe identifyitearly,treatit,reducesufferingandrehabi- done.Manyclinicians‘struggletoapplytheresultsof litatepeopletonormallifepresentsachallengewhich studies that do not seem that relevant to their daily cannotbeignored. practice’.4RCTshaveanumberofstrongpointsbut the ready generalization of their results to ‘real life’ clinical situations is not one of them. Too strong an Evidence-based diabetes practice emphasisontheneedforevidencetosupportpractice can easily be translated into an unwillingness to do Diabetesisaparticularlygoodexampleofthepoten- anything which is not based on evidence. Thus the tialforevidence-basedpractice.Thereareatleastfour 2 CHAPTER 1 Theevidencebasefordiabetescare 1 The person with diabetes is central to the management of the condition 2 Diabetes care is multidisciplinary – evidence-based practice is important 3 The worldwide impact of diabetes is increasing at a dramatic rate 4 There is a considerable quantity of high-quality evidence available Figure1.1 Thepotentialofdiabetesforevidence-basedpractice reasonsforthis(Figure1.1).First,mostdiabetescareis Thefollowingratescanbedefined: basedonlong-termbehaviouralchange.Suchchange willnottakeplaceunlesstheaffectedpersoniswilling Experimentaleventrate(EER)¼A/(AþB) tomakethesechangesandisassistedinmakingthese Controleventrate(CER)¼C/(CþD) changes. What better way is there of encouraging Absoluteriskreduction(ARR)¼CER(cid:2)EER evidence-based practice than to make both patients Relativeriskreduction(RRR)¼(CER(cid:2)EER)/CER andpractitionersawareoftheevidencethatexistsand Numberneededtotreat(NNT)¼1/ARR thebenefits(andharms)ofimplementingit?Second, diabetes care is multidisciplinary. The person with Analogous calculations can be performed in rela- diabetesand,inmostinstances,thefamily,areatthe tiontoadverseevents: centre of all diabetes health care activities. To be successful,diabetescareneedstoinvolvethecoopera- Adverseevent tionandcollaborationofmanypractitioners–nurses, dieticians, podiatrists, psychologists and doctors. Present Notpresent Thusdiabetescareisaparticularlystrikingexample Intervention A B AþB of evidence-based practice as opposed to evidence- group based medicine. Third, the increasing prevalence of Controlgroup C D CþD diabetesanditspublichealthimportance,particularly indevelopingcountries,areamajorimpetusforthis book.Finally,thereisaconsiderablequantityofhigh- Experimental (adverse) event rate (E(A)ER)¼A/ qualityevidencerelevanttodiabetespreventionand (AþB) carethatneedstobetranslatedintopractice.Aswith Control(adverse)eventrate(C(A)ER)¼C/(CþD) otherfields,thereisalsoevidencewhichisnotofsuch Absoluteriskofadverseevents¼E(A)ER(cid:2)C(A)ER highqualityandareasforwhichlittleevidenceexists Relative risk of adverse events¼(E(A)ER(cid:2)C(A) atall. ER)/C(A)ER Number treated for one adverse event¼1/absolute riskofadverseevent A brief explanation of terms Bothabsoluteandrelativeriskmeasureshavetheir Throughoutthisbook,variousepidemiologicalterms place in evidence-based practice, but in order to have been used to describe risk in the context of understand relative risk measures, knowledge of clinicaltrials.Thesecanbesummarizedasfollowsin what they are relative to is needed. For example, a relation to a trial which randomizes participants to relativeriskreductionof50%couldmeangoingfrom two groups – an intervention group and a control anabsoluteriskof1%to0.5%orfromanabsoluterisk group.Imagine,forthesakeofsimplicity,twodichot- of20%to10%.However,theabsoluteriskreductions, omous outcomes – prevention and non-prevention, which in this case would be 0.5% and 10%, respec- forexample: tively, demonstrate markedly different benefits. When available, authors have been encouraged to include absolute measures, with or without their Outcome relativeequivalents. Prevention Non- prevention The hierarchy of evidence Intervention A B AþB There are several suggested hierarchies for grading group Controlgroup C D CþD evidence.Examplesoftwoofthesearethatusedby the United States Preventive Services Task Force 3